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 there is another which varies with each new perception, and even with every moment of the same perception—that is to say, the object. It is not impossible to understand that the consciousness remains deaf to the constant and sensitive to the variable element. There is a law of consciousness which has often been described, and fresh applications of which are met with daily: this is, that the consciousness only maintains itself by change, whether this change results from the exterior by impressions received, or is produced from the interior by movements of the attention. Let us here apply this empirical law, and admit that it contains a first principle. It will then be possible for us to understand that the consciousness formed into a dialyser of the undulation may reject that constant element which expresses the contribution of the nervous system, and may lay bare the variable element which corresponds to the object: so that an intestinal movement of the cerebral substance, brought to light by this analytical consciousness, may become the perception of an object. By accepting this hypothesis, we restore to the sensory nerves and to the encephalic centres their property of being the substrata of representation, and avoid the objection made above against materialism and parallelism, that they did not explain how a cerebral movement, which is material, can engender the perception of an object which differs